1. Field of the Invention
The present invention relates to a heat transfer recording apparatus which transfers ink from an ink sheet to a recording medium in order to record images on the recording medium and to a facsimile using the same.
2. Description of the Related Art
In heat transfer printers, generally, an ink sheet with a heat meltable (heat sublimable) ink applied on a base film is used. Heat transfer printers record images in such a way that the ink sheet is selectively heated by a thermal head in response to an image signal and the molten (sublimed) ink is transferred to recording paper. Since this ink sheet is usually the type in which ink is completely transferred onto recording paper after one image recording (a so-called one-time sheet), after one character or one line is recorded, the ink sheet must be conveyor by a distance corresponding to the length of the recording so as to reliably bring an unused portion of the ink sheet to a position at which recording will be made next. As a result, the amount of ink sheet used is increased, and the running cost of heat transfer printers is likely to be higher than that of thermal printers which print on thermal paper.
To solve such problems, a heat transfer printer in which the transport speed of recording paper is made to differ from that of an ink sheet has been proposed, as disclosed in Japanese Patent Laid-Open Nos. 57-83471, 58-201686, and 62-58917.
There is a known ink sheet (the so-called multiprint sheet) with which plural (n times) image recording operations are possible. The use of this ink sheet enables recording in the state in which the transport length of an ink sheet transported after image recording for each line or during image recording is made smaller than a length L (L/n: n&gt;1) when recording is continuously made at the recording length L. Therefore, the efficiency of the use of ink sheets is increased by a factor of n over the previous efficiency and the running cost of heat transfer printers can be expected to be lowered. Hereinafter, this recording method is called the multiprint recording method.
When an ink sheet is used with the multiprint method, the ink of the ink layer of the ink sheet is divided into n parts and heated n times. A shearing force is generated, during each of these heating operations, between the molten (sublimed) ink of the ink layer and the ink which has not been melted (sublimed), and transfer is performed on recording paper. For this reason, for example, if the ink cools because the time between recording of the next line after the recording for one line becomes long, a problem arises in that a shearing force between the molten (sublimed) ink of the ink layer and the ink which has not been molten (sublimed) becomes larger and the ink sheet is difficult to separate from the recording paper. This problem becomes conspicuous when one line of record data contains black data. This also becomes a problem in an apparatus like a facsimile, in which the interval of recording time between the current line and the next line is not fixed and the overall intervals of recording times are relatively longer.